In machines such as centrifugal pumps with rotating shafts, it is frequently necessary to obtain an effective seal between the rotating shafts and stationary elements of the machine. These rotating shaft seals may find particular application in bearing housings to prevent lubricants, used to lubricate bearing elements such as ball and thrust bearings, from leaking out of the housing. Another important function of the rotating shaft seals for bearing housings is to prevent contaminants, such as dirt, dust, water, pump leakage and condensation from entering the bearing housing.
The entrance of contaminants within a bearing housing can pose a serious threat to the lubricating fluid contained therein. Should contaminants enter a bearing housing, the lubrication of the bearings by the lubricating fluid can be substantially impaired. A loss of lubrication may cause bearings to operate at excessive temperatures, which can lead to premature failure of the bearings and subsequent failure of the pump or other device that the bearing housing is incorporated into.
The escape of lubricants from the bearing housing through the shaft seals is capable of causing similar problems. Frequent servicing may be required to replace escaping lubricants. Also, the leakage of lubricant from the bearing housing may cause an inadequate amount of lubrication fluid in the housing such that excessive wear will take place, which can eventually cause premature bearing failure.
One type of sealing device used to provide a seal about rotating shafts and particularly about shafts extending through bearing housings are mechanical labyrinth seals. These seals commonly incorporate a rotating element or rotor and a stationary element or stator. In the labyrinth seal, opposing faces of the stator and rotor are configured to form a maze or labyrinth flow path along an interface between the rotor and stator. In addition, the opposing faces are machined to a tight tolerance so that the separation or gap between the opposing faces of the rotor and stator is very narrow. The labyrinth path created by the labyrinth sealing elements and narrow separation inhibits the leakage of lubricants between the rotating rotor and stationary stator and out of the seal. Similarly, the labyrinth inhibits the entrance of contaminants into the bearing through the rotor and stator.
Seals between the labyrinth rotor and shaft and between the labyrinth stator and bearing housing are commonly provided by the use of O-rings and O-ring grooves. The O-ring seal between the shaft and rotor may also function to affix the rotor to the shaft.
One of the major problems with labyrinth seals is for the seals to provide an effective seal while maintaining the narrow separation along the interface between the faces of the stator and rotor during rotation of the shaft. Should the rotor separate from the stator, and the separation along the interface between the faces increase even slightly, lubricants and/or contaminants may flow freely through the interface between the rotor and stator thus negating the sealing capability of the seal. Numerous factors may lead to this type of separation, such as vibration, improper maintenance of the machine and seal, and improper installation of the seal or shaft.
Solutions to address this problem have included various methods for locking a rotor and stator together. Some methods utilized additional O-rings, additional locking rings of various materials, and means introducing additional parts into the seal. The employment of additional parts can increase the complexity and unreliability of the seal as well as the cost of manufacture.